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Old 21st August 2003, 05:36 AM   #1
deyton is offline deyton  Canada
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Default Peerless CSX vs Vifa MG?

Is either substantially better? I'm debating which to get, as i can get the MG's for only 8 bucks more canadian. This is the 7" MG vs. 7" CSX (not the car one, the 4 ohm home version, 850123). I listen mainly to mostly rock and hard rock, with a little metal and rap sprinkled in between, if that makes a difference, and they will be paired with probably an LPG 26na, maybe a 25nfa. Right now I'm leaning towards the MG and 26NA, what are the advantages/disadvantages?
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Old 22nd August 2003, 04:01 AM   #2
deyton is offline deyton  Canada
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I recently found a good deal at partsexpress on vifa PL's, i'm assuming they would be a step up on both?

C'mon, i know someone knows, cause it sure looks like a pair of MG's on the main DIYaudio page
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Old 22nd August 2003, 12:37 PM   #3
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The Peerless CSX line, as well as other, (not all) Peerless lines, has an aluminum shorting ring, or Faraday ring, in the voice coil. This gives it a symmetrical magnetic field.

The Vifa does not mention either one. Therefore, we can assume it does not have it.

The significance of the symmetrical magnetic field is that in a bass reflex enclosure, when the frequency approached the tuned frequency of the box, the speaker actually leaves the center of the gap and moves all the way to the end of it's travel. Instead of staying in the middle, it moves all the way to the extreme, and moves back-and-forth from there. Since it's starting point is the end of the line, so to speak, this essentially shears off half the waveform. If you run a tone generator through a bass reflex speaker, as you approach the tuned frequency of the box, you can see this happen right before your eyes.

Theoretically, the same phenomenon should occur in a sealed box. However, I have never seen that happen in a sealed box, only ported ones.

Sometimes this phenomenon is stated as "high second harmonic distortion", but that phrase does not do justice to what is occurring.

The Faraday ring, which Peerless has, prevents this. The other way to prevent this is to use an extended pole piece,or an extended core. That also gives a symmetrical magnetic field.


The Vifa mentions neither of these. Since these provide an important benefit, we should therefore assume that it does not have them.

If you are going to use these in a ported box, this gives the Peerless a large edge. In fact, I would not build a ported box using a woofer that did not have a symmetrical magnetic field-that is, either a Faraday ring or an extended pole piece.
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Old 27th August 2003, 03:02 AM   #4
deyton is offline deyton  Canada
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Quote:
Originally posted by kelticwizard
The Peerless CSX line, as well as other, (not all) Peerless lines, has an aluminum shorting ring, or Faraday ring, in the voice coil. This gives it a symmetrical magnetic field.

The Vifa does not mention either one. Therefore, we can assume it does not have it.

The significance of the symmetrical magnetic field is that in a bass reflex enclosure, when the frequency approached the tuned frequency of the box, the speaker actually leaves the center of the gap and moves all the way to the end of it's travel. Instead of staying in the middle, it moves all the way to the extreme, and moves back-and-forth from there. Since it's starting point is the end of the line, so to speak, this essentially shears off half the waveform. If you run a tone generator through a bass reflex speaker, as you approach the tuned frequency of the box, you can see this happen right before your eyes.

Theoretically, the same phenomenon should occur in a sealed box. However, I have never seen that happen in a sealed box, only ported ones.

Sometimes this phenomenon is stated as "high second harmonic distortion", but that phrase does not do justice to what is occurring.

The Faraday ring, which Peerless has, prevents this. The other way to prevent this is to use an extended pole piece,or an extended core. That also gives a symmetrical magnetic field.


The Vifa mentions neither of these. Since these provide an important benefit, we should therefore assume that it does not have them.

If you are going to use these in a ported box, this gives the Peerless a large edge. In fact, I would not build a ported box using a woofer that did not have a symmetrical magnetic field-that is, either a Faraday ring or an extended pole piece.
Thanks, because i was planning on using a ported box for sure. I think the peerless is the way to go (I'm actually getting it significantly cheaper now as well).
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Old 27th December 2003, 10:56 AM   #5
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What if the use was for a midrange driver? Does the shorting ring have any advantage then? In that application, which driver would be better?

Any experience with these drivers anyone?
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Old 27th December 2003, 09:07 PM   #6
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From what I have read, the shorting ring, (but not the extended pole piece), improves things into the midrange. I don't know how, but apparently there is consensus that it does.
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Old 27th December 2003, 09:46 PM   #7
Thunau is offline Thunau  United States
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Quote:
Originally posted by kelticwizard


The significance of the symmetrical magnetic field is that in a bass reflex enclosure, when the frequency approached the tuned frequency of the box, the speaker actually leaves the center of the gap and moves all the way to the end of it's travel. Instead of staying in the middle, it moves all the way to the extreme, and moves back-and-forth from there. Since it's starting point is the end of the line, so to speak, this essentially shears off half the waveform. If you run a tone generator through a bass reflex speaker, as you approach the tuned frequency of the box, you can see this happen right before your eyes.

Theoretically, the same phenomenon should occur in a sealed box. However, I have never seen that happen in a sealed box, only ported ones.

Sometimes this phenomenon is stated as "high second harmonic distortion", but that phrase does not do justice to what is occurring.

The Faraday ring, which Peerless has, prevents this. The other way to prevent this is to use an extended pole piece,or an extended core. That also gives a symmetrical magnetic field.


The Vifa mentions neither of these. Since these provide an important benefit, we should therefore assume that it does not have them.

If you are going to use these in a ported box, this gives the Peerless a large edge. In fact, I would not build a ported box using a woofer that did not have a symmetrical magnetic field-that is, either a Faraday ring or an extended pole piece.


The effect of the speaker cone not centering under certain conditions has little to do with the box being ported or sealed. As a matter of fact in a bass reflex box the cone excursion is smallest at the resonant frequency of the box/port combo. Below the tuning frequency of the box the speaker has little resistance and it tends to unload and reach it's max excursion easily. It is possible that you have seen this effect at frequencies below port tuning.
The effect of the cone being "sucked-in" has to do with magnetic saturation and can be achieved using a wide range of frequencies in free air.
I have seen it while testing a Dynaudio 12" woofer with a 1000Hz signal. Once a certain signal level is reached the cone gets sucked in and the tone starts to compress (increase of the input results in non linear increase of the output).

The Faraday rings will help minimise that effect regardless of the application- sealed, vented or open baffle.
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Old 27th December 2003, 11:06 PM   #8
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Thunau:

With all respect, the "suck-in" phenomenon was observed by myself in a ported box at frequencies a significant portion of an octave above resonance down to resonance.

D.B. Keele has written articles on the phenomenon in Audio magazine, and I believe elsewhere. He made it clear that the way to combat it was to use either a Faraday ring or an extended pole piece. As he explained it, the effect is because there is more magnetic material on one side of the voice coil than on the other.

A Faraday ring prevents this, though I never did follow the the explanation as to how. But a Faraday ring somehow shortens the magnetic field. I am not an engineer. I can only tell you that it works.

The effect I saw on the woofers was about 10 or 12 years ago, and the articles by Keele a short time after. I am given to understand there is possibly a third alternative, where the part of the pole piece near the end plate is reduced in diameter, but returns to full diameter when in the magnetic gap. This is the method used by JBL, McCauley, and possibly others.

But the suck-in phenomenon did occur at resonance and somewhat above resonance. I have read that it can occur in sealed boxes as well, though I have not observed it in the sealed boxes I have built.

PS: It is true that cone excursion is reduced just above and at resonance, although seemingly not as much as the simulations show. However, the center of that reduced movement moves back into the speaker. This is visible, and no doubt is the reason for the name "suck-in". I understand it is also called "oil-canning".
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Old 27th December 2003, 11:49 PM   #9
sreten is offline sreten  United Kingdom
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KC,

I'm sorry but you need to get your facts absolutely straight
before you make such apparently unequivocal statements.

I'm pretty sure you don't have the facts straight.
(And here is not the place to argue about it)

IMO I'm sorry to say this is thread 'highjacking' by any definition.

Deyton,

the important thing is to find a good design that uses the drivers
you are considering, let someone else do all the difficult and hard
work.

If your taken by the PL18's you can't go too far wrong with :

http://www.speakerbuilder.net/web_fi...ct/erosmk2.htm
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Old 28th December 2003, 04:28 AM   #10
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Sreten,

know any good designs using the Vifa MG drivers? (especially MTM)? or the CSX for that matter?
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